objective c - Difference between "Use auto layout" and "Use size class" in xcode 6.1?

Question

What is the difference between the "Use auto layout" and "Use size class" on storyboards in xcode 6.1?

Answer 1

“Auto Layout is a system that lets you lay out your app’s user interface by creating a mathematical description of the relationships between the elements. You define these relationships in terms of constraints either on individual elements, or between sets of elements.”

Size Classes let you set different constraints for certain screen sizes. This let’s you go beyond basic stretching layouts.In Xcode 6 Apple introduced Size Classes.